Nitrogen Removal Mechanism of Fresh Leachate Treatment Using Sequencing Aged Refuse Bioreactors

In this study, the aged refuse excavated from a 10-year old closed landfill compartment at Shanghai Laogang Refuse Landfill was used as the substrate in a sequencing aged refuse bioreactor process for treatment of fresh landfill leachate which sampled from the balance tank in the same landfill. Typically, screened aged refuse with a diameter less than 8 mm was used as bio-filtration material in the two round shaped bioreactor with an inner diameter of 40 cm and a height of 130 cm. Influent fresh leachate with initial COD_Cr, TN and NH₃-N concentrations of 11000~15000, 1340~1770 and 11200~1650 mg/L, respectively, was introduced into the system. The corresponding concentrations in the effluent were reduced to below 300, about 250, and below 15 mg/L, respectively. The sequencing aged refuse process is effective in the fresh leachate treatment, the removal efficiency of COD and TN removal is about 90% and 80% respectively, and the ammonia nitrogen transformation efficiency is about 99.5%. The treatment mechanism of nitrogen removal was studied. In the process, the nitrogen removal is mainly due to the simultaneous nitrification and denitrification in both bioreactors. Recirculated nitrate nitrogen denitrification exists in bioreactor 1, but is not the main nitrogen removal pathway, which is different from the nitrogen removal mechanism in aged leachate treatment.